Plasma etch-resistant film and a method for its fabrication

ABSTRACT

The invention relates to a method for fabricating a plasma etch-resistant film (1) on a surface of a substrate (2), wherein the method comprises the step of forming a film comprising an intermediate layer (4) of rare earth metal oxide, rare earth metal carbonate, or rare earth metal oxycarbonate, or anymixture thereof on a first layer (3) of rare earth metal oxide, wherein the rare earth metal is the same in the first layer and in the intermediate layer. The invention further relates to a plasma etch-resistant film and to the use thereof.

FIELD OF THE INVENTION

The invention relates to a method for fabricating a plasmaetch-resistant film on a surface of a substrate. The invention furtherrelates to a plasma etch-resistant film on a surface of a substrate. Theinvention further relates to the use of a plasma etch-resistant film.

BACKGROUND OF THE INVENTION

The surfaces and components of a plasma reaction chamber are subjectedto harsh conditions during the employed process. The resistance toplasmas is thus a desirable property for components used in processingchambers where corrosive environments are present. Therefore, protectingcomponents against such corrosive environment is desired in order toprolong the lifetime of the used components or chambers. To reduce theerosion or degradation of the surfaces exposed to the corrosiveenvironment, thick coatings or films of e.g. aluminium oxide have beenformed on the surfaces that are to be protected. The aim of suchcoatings or films is to act to reduce exposure of the surface to beprotected to various plasmas such as NF₂, CF₄, CHF₃, CH₂F₂, C₂F₆, SF₆,Cl₂ and HBr. However, although these coatings or films exhibit improvedplasma resistance they often have porous structure as a result of e.g.the used fabrication method. Thus, with time, the porous structureallows the adverse effects of the corrosive environment to penetratethrough the coating to the surface to be protected and/or to form solidparticles that contaminate the surroundings. Also, thick films mayeasily crack whereby its protective effect is easily lost.

Thus, there remains a need for a method enabling to fabricate along-lasting plasma etch-resistant film with properties suitable forprotecting e.g. the surfaces of a plasma chamber and components thereofagainst the detrimental processing conditions.

PURPOSE OF THE INVENTION

The purpose of the invention is to provide a new type of method forfabricating a plasma etch-resistant film on a surface of a substrate.Further, the purpose of the invention is to provide a new type of aplasma etch-resistant film and to provide a new use of the plasmaetch-resistant film.

SUMMARY

The method according to the present invention is characterized by whatis presented in claim 1.

The plasma etch-resistant film according to the present invention ischaracterized by what is presented in claims 14 and 15.

The use according to the present invention is characterized by what ispresented in claim 19.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and constitute a part of thisspecification, illustrate embodiments of the invention and together withthe description help to explain the principles of the invention. In thedrawings:

FIG. 1 a flow-chart illustration of a method according to one embodimentof the present invention;

FIG. 2 is a schematic illustration of a plasma etch-resistant film on asubstrate according to one embodiment of the present invention; and

FIG. 3 is a cross sectional field emission scanning electron microscope(FE-SEM) image of a plasma etch-resistant film according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for fabricating a plasmaetch-resistant film on a surface of a substrate, wherein the methodcomprises the step of forming a film comprising an intermediate layer ofrare earth metal oxide, rare earth metal carbonate, or rare earth metaloxycarbonate, or any mixture thereof on a first layer of rare earthmetal oxide, wherein the rare earth metal is the same in the first layerand in the intermediate layer, and wherein the step of forming the filmcomprises, in a reaction space, the steps of:

depositing the first layer by exposing a deposition surface toalternately repeated surface reactions of at least two precursorsincluding a precursor for rare earth metal and a first precursor foroxygen such that the structure of the first layer is crystalline, and

depositing the intermediate layer by exposing a deposition surface toalternately repeated surface reactions of at least two precursorsincluding a precursor for rare earth metal and a second precursor foroxygen such that the structure of the intermediate layer is amorphous.

The present invention further relates to a plasma etch-resistant film ona surface of a substrate obtainable by a method according to the presentinvention.

The present invention further relates to a plasma etch-resistant film ona surface of a substrate, wherein the film comprises an intermediatelayer of rare earth metal oxide, rare earth metal carbonate, or rareearth metal oxycarbonate, or any mixture thereof deposited on a firstlayer of rare earth metal oxide, wherein the rare earth metal is thesame in the first layer and in the intermediate layer, and wherein thestructure of the first layer is crystalline and the structure of theintermediate layer is amorphous.

The present invention further relates to a plasma etch-resistant film ona surface of a substrate, wherein the film comprises an intermediatelayer of rare earth metal oxide, rare earth metal carbonate, or rareearth metal oxycarbonate, or any mixture thereof deposited on a firstlayer of rare earth metal oxide, wherein the rare earth metal in theintermediate layer is different from the rare earth metal in the firstlayer, and wherein the structure of the first layer is crystalline andthe structure of the intermediate layer is amorphous.

The present invention further relates to a method for fabricating aplasma etch-resistant film on a surface of a substrate, wherein themethod comprises the step of forming a film comprising an intermediatelayer of rare earth metal oxide, rare earth metal carbonate, or rareearth metal oxycarbonate, or any mixture thereof on a first layer ofrare earth metal oxide, wherein the rare earth metal is different in thefirst layer and in the intermediate layer, and wherein the structure ofthe first layer is crystalline and the structure of the intermediatelayer is amorphous.

The present invention further relates to a plasma etch-resistant film ona surface of a substrate, wherein the film comprises an intermediatelayer of aluminium oxide and/or silicon dioxide, deposited on a firstlayer of rare earth metal oxide, wherein the structure of the firstlayer is crystalline and the structure of the intermediate layer isamorphous.

The present invention further relates to a method for fabricating aplasma etch-resistant film on a surface of a substrate, wherein themethod comprises the step of forming a film comprising an intermediatelayer of aluminium oxide and/or silicon dioxide on a first layer of rareearth metal oxide, wherein the structure of the first layer iscrystalline and the structure of the intermediate layer is amorphous.

The present invention further relates to the use of the plasmaetch-resistant film according to the present invention for protecting asurface of a plasma chamber against the detrimental effects of theprocessing conditions used in the plasma chamber. The present inventionfurther relates to the use of the plasma etch-resistant film accordingto the present invention for protecting a surface of a plasma chamber.

The rare earth metal oxide of the first layer is crystalline rare earthmetal oxide. The rare earth metal oxide of the intermediate layer isamorphous rare earth metal oxide. The rare earth metal carbonate of theintermediate layer is amorphous rare earth metal carbonate. The rareearth metal oxycarbonate of the intermediate layer is amorphous rareearth metal oxycarbonate. The rare earth metal oxide, the rare earthmetal carbonate, or the rare earth metal oxycarbonate of theintermediate layer is amorphous rare earth metal oxide, rare earth metalcarbonate, or rare earth metal oxycarbonate.

The first precursor for oxygen is different from the second precursorfor oxygen. The inventors of the present invention surprisingly foundout that by changing the precursor for oxygen during the process ofdepositing the plasma etch-resistant film, the structure of the formedlayer can be changed in order to enable so-called intermediate layers orcut-off layers to be formed in the film without the need to introduceany layers of different materials in the plasma etch-resistant film.These intermediate layers have the effect of controlling thecrystallinity and crystallite phases and hindering the harmfulcrystalline growth orientation of the following first layer of rareearth metal oxide which results in a final plasma etch-resistant filmhaving a dense or non-porous structure. The dense or non-porousstructure has the added utility of hindering propagation of possiblecracks. Such a dense or non-porous structure has the technical effect ofbeing able to resist cracking or delamination from the surface of thesubstrate. I.e. the amorphous intermediate layer formed on a crystallinefirst layer results in that the growth direction of the crystals in thefollowing first layer will not alter compared to the growth direction ofthe preceding first layer. Without limiting the present invention to anyspecific theory, the inventors of the present invention surprisinglyfound out that the formation of a monoclinic phase of rare earth metaloxide, which may lead to cracking or delamination of the plasmaetch-resistant film, can be reduced or avoided by forming one or moreintermediate layers of rare earth metal oxide, rare earth metalcarbonate, or rare earth metal oxycarbonate, or any mixture thereof withthe method according to the present invention.

In one embodiment, the structure of the first layer comprises at least50 weight-% of the crystalline (222) orientation of the rare earth metaloxide. In one embodiment, the structure of the first layer comprises atleast 50 weight-% of the crystalline (440) orientation of the rare earthmetal oxide. In one embodiment, the structure of the first layercomprises at least 50 weight-% of a combination of the crystalline (222)orientation and the crystalline (440) orientation of the rare earthmetal oxide.

In this specification, unless otherwise stated, the term “the surface”,“surface of the substrate”, or “deposition surface” is used to addressthe surface of the substrate or the surface of the already formed layeror deposit on the substrate. Therefore, the terms “surface”, “surface ofthe substrate” and “deposition surface” include the surface of thesubstrate which has not yet been exposed to any precursors and thesurface which has been exposed to one or more precursors. The“deposition surface” thus changes during the deposition process, whenchemicals get adsorbed onto the surface.

In one embodiment, the substrate material is selected from a groupconsisting of aluminum metal, anodized aluminum metal, stainless steeland quartz.

In one embodiment, the substrate material is selected from a groupconsisting of aluminum metal, stainless steel and quartz pre-coated withaluminium oxide or yttrium oxide formed by any other deposition methodthan the ALD-type method.

In one embodiment, the first layer and the intermediate layer arefabricated on the deposition surface by an ALD-type process. When thefirst layer and the intermediate layer are fabricated on the surface ofthe substrate by an ALD-type process excellent conformality anduniformity is achieved for the passivation layer.

The ALD-type process is a method for depositing uniform and conformaldeposits or layers over substrates of various shapes, even over complexthree dimensional structures. In the ALD-type process, the substrate isalternately exposed to at least two different precursors (chemicals),usually one precursor at a time, to form on the substrate a deposit or alayer by alternately repeating essentially self-limiting surfacereactions between the surface of the substrate (on the later stages,naturally, the surface of the already formed layer on the substrate) andthe precursors. As a result, the deposited material is “grown” on thesubstrate molecule layer by molecule layer.

The distinctive feature of the ALD-type process is that the surface tobe deposited is exposed to two or more different precursors in analternate manner with usually a purging period in between the precursorpulses. During a purging period the deposition surface is exposed to aflow of gas which does not react with the precursors used in theprocess. This gas, often called the carrier gas is therefore inerttowards the precursors used in the process and removes e.g. surplusprecursor and by-products resulting from the chemisorption reactions ofthe previous precursor pulse. This purging can be arranged by differentmeans. The basic requirement of the ALD-type process is that thedeposition surface is purged between the introduction of a precursor fora metal and a precursor for a non-metal. The purging period ensures thatthe gas phase growth is limited and only surfaces exposed to theprecursor gas participate in the growth. However, the purging step withan inert gas can, according to one embodiment of the present invention,be omitted in the ALD-type process when applying two process gases, i.e.different precursors, which do not react with each other. Withoutlimiting the present invention to any specific ALD-cycle, it can bementioned, as an example only, that the purging period can be omittedbetween two precursors, which do not react with each other. I.e. thepurging period can be omitted, in some embodiments of the presentinvention, e.g. between two different precursors for oxygen if they donot react with each other.

The alternate or sequential exposure of the deposition surface todifferent precursors can be carried out in different manners. In a batchtype process at least one substrate is placed in a reaction space, intowhich precursor and purge gases are being introduced in a predeterminedcycle. Spatial atomic layer deposition is an ALD-type process based onthe spatial separation of precursor gases or vapors. The differentprecursor gases or vapors can be confined in specific process areas orzones while the substrate passes by. In the continuous ALD-type processconstant gas flow zones separated in space and a moving substrate areused in order to obtain the time sequential exposure. By moving thesubstrate through stationary zones, providing precursor exposure andpurging areas, in the reaction space, a continuous coating process isachieved enabling roll-to-roll coating of a substrate. In continuousALD-type process the cycle time depends on the speed of movement of thesubstrate between the gas flow zones.

Other names besides atomic layer deposition (ALD) have also beenemployed for these types of processes, where the alternate introductionof or exposure to two or more different precursors lead to the growth ofthe layer, often through essentially self-limiting surface reactions.These other names or process variants include atomic layer epitaxy(ALE), atomic layer chemical vapour deposition (ALCVD), andcorresponding plasma enhanced variants. Unless otherwise stated, alsothese processes will be collectively addressed as ALD-type processes inthis specification.

In one embodiment, the method comprises depositing the intermediatelayer on the first layer such that the surface of the first layer iscovered by the intermediate layer.

In one embodiment, the deposition surface is exposed to carbon dioxidesimultaneously with being exposed to the second precursor for oxygen orafter being exposed to the second precursor for oxygen. The presence ofthe carbon dioxide during the step of depositing the intermediate layerenables or enhances the formation of rare earth metal carbonate or rareearth metal oxycarbonate.

In this specification, unless otherwise stated, the term “rare earthmetal oxycarbonate” is used to address any rare earth metal substancewhich is both an oxide and a carbonate.

In one embodiment, the first precursor for oxygen is selected from agroup consisting of water and an alcohol. In one embodiment, the firstprecursor for oxygen is selected from a group consisting of water,methanol, ethanol, propanol, isopropanol, butanol, 2-butanol, andtert-butanol. In one embodiment, the first precursor for oxygen iswater.

In one embodiment, the second precursor for oxygen is selected from agroup consisting of ozone; a combination of ozone and water; acombination of ozone and oxygen; a combination of ozone and hydrogenperoxide; oxygen-containing radicals; oxygen plasma; carbon dioxideplasma; organic peroxides; organic hydroperoxides; peroxyacids; andsinglet oxygen.

In one embodiment, the second precursor for oxygen is ozone. In oneembodiment, the second precursor for oxygen is selected from a groupconsisting of ozone; and a combination comprising ozone.

In one embodiment, the second precursor for oxygen is selected from agroup consisting of a combination of ozone and water; a combination ofozone and oxygen; and a combination of ozone and hydrogen peroxide.

In one embodiment, the second precursor for oxygen is selected from agroup consisting of oxygen-containing radicals; oxygen plasma; carbondioxide plasma; organic peroxides; organic hydroperoxides; peroxyacids;and singlet oxygen.

Examples of an oxygen-containing radical are O* and *OH, wherein *denotes an unpaired electron. By organic peroxides are herein meantorganic compounds containing the peroxide functional group R′—O—O—R″,wherein R′ and R″ each independently denote moieties, e.g. hydrocarbonmoieties. By organic hydroperoxides are herein meant the organiccompounds containing the functional group R—O—O—H, wherein R denotes amoiety, e.g. a hydrocarbon moiety. By peroxyacids is herein meant thecompounds containing the functional group R(CO)OOH, wherein R denotes amoiety, e.g. a hydrocarbon moiety. By singlet oxygen is herein meant theelectronically excited state of molecular oxygen (O₂(a¹Δ_(g))). The useof the above precursors as the second precursor for oxygen has the addedutility of enabling the formation of an intermediate layer, which has anamorphous structure.

In one embodiment, the precursor for rare earth metal is selected from agroup consisting of a precursor for scandium, a precursor for yttrium, aprecursor for lanthanum, a precursor for cerium, a precursor forpraseodymium, a precursor for neodymium, a precursor for samarium, aprecursor for europium, a precursor for gadolinium, a precursor forterbium, a precursor for dysprosium, a precursor for holmium, aprecursor for erbium, a precursor for thulium, a precursor forytterbium, and a precursor for lutetium. In one embodiment, theprecursor for rare earth metal is a precursor for yttrium.

In one embodiment, the precursor for rare earth metal is selected from agroup consisting of vaporizable water-reactive compounds of rare earthmetals. In one embodiment, the precursor for rare earth metal isselected from a group consisting of vaporizable substituted orunsubstituted partially unsaturated carbocyclic compounds of rare earthmetals. In one embodiment, the precursor for rare earth metal isselected from a group consisting of substituted or unsubstitutedcyclopentadienyl compounds of rare earth metals. In one embodiment, theprecursor for rare earth metal is selected from a group consisting ofsubstituted or unsubstituted cycloheptatrienyl compounds of rare earthmetals. In one embodiment, the precursor for rare earth metal isselected from a group consisting of substituted or unsubstitutedcyclooctadienyl compounds of rare earth metals. In one embodiment, theprecursor for rare earth metal contains at least one ligand selectedfrom a group consisting of substituted or unsubstitutedcyclopentadienyl, cycloheptadienyl, and cyclooctadienyl. In oneembodiment, the precursor for rare earth metal is preferably acyclopentadienyl or substituted cyclopentadienyl compound of yttrium,and more preferably tris(methylcyclopentadienyl)yttrium.

In one embodiment, the steps of depositing the first layer anddepositing the intermediate layer are carried out by using the sameprecursor for rare earth metal, or the steps of depositing the firstlayer and depositing the intermediate layer are carried out by usingdifferent precursors for rare earth metal.

In one embodiment, the rare earth metal is selected from a groupconsisting of scandium, yttrium, lanthanum, cerium, praseodymium,neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium,erbium, thulium, ytterbium, and lutetium.

In one embodiment, the rare earth metal is yttrium.

In one embodiment, the rare earth metal oxide of the first layer and ofthe intermediate layer is selected from a group consisting of Sc₂O₃,Y₂O₃, La₂O₃, CeO₂, Ce₂O₃, PrO₂, Pr₂O₃, Nd₂O₃, NdO, Sm₂O₃, SmO, Eu₂O₃,EuO, Eu₃O₄, Gd₂O₃, TbO₂, Tb₂O₃, Dy₂O₃, Ho₂O₃, Tm₂O₃, Yb₂O₃, YbO, Lu₂O₃,and any combination thereof.

In one embodiment, the rare earth metal carbonate of the intermediatelayer contains at least one inorganic carbonate group CO₃.

In one embodiment, the rare earth metal carbonate of the intermediatelayer is selected from a group consisting of Sc₂(CO₃)₃. Y₂(CO₃)₃,La₂(CO₃)₃, Ce₂(CO₃)₃, Pr₂(CO₃)₃, Nd₂(CO₃)₃, Sm₂(CO₃)₃, Eu₂(CO₃)₃,Gd₂(CO₃) ₃, Tb₂(CO₃)₃, Dy₂ (CO₃) ₃, Ho₂(CO₃)₃, Er₂(CO₃)₃, Tm₂(CO₃)₃,Yb₂(CO₃)₃, Lu₂(CO₃)₃, and any combination thereof.

In one embodiment, the rare earth metal oxycarbonate of the intermediatelayer is selected from a group consisting of Sc₂O₂CO₃, Sc₂O(CO₃)₂,Y₂O₂CO₃, Y₂O(CO₃)₂, La₂O₂CO₃, La₂O(CO₃)₂, Ce₂O(CO₃)₂, Ce₂O₂CO₃, CeOCO₃,Pr₂O₂CO₃, Pr₂O(CO₃)₂, Nd₂O₂CO₃, Nd₂O(CO₃)₂, Sm₂O₂CO₃, Sm₂O(CO₃)₂,Eu₂O₂CO₃, Eu₂O(CO₃)₂, Gd₂O₂CO₃, Gd₂O(CO₃)₂, Tb₂O₂CO₃, Tb₂O(CO₃)₂,Dy₂O₂CO₃, Dy₂O(CO₃)₂, HO₂O₂CO₃, Ho₂O(CO₃)₂, Er₂O₂CO₃, Er₂O(CO₃)₂,Tm₂O₂CO₃, Tm₂O(CO₃)₂, YbO₂CO₃, Yb₂O₂O(CO₃)₂, Lu₂O₂CO₃, Lu₂O(CO₃)₂, andany combination thereof.

In one embodiment, the steps of depositing the first layer anddepositing the intermediate layer are carried out in the sametemperature or temperature range. In one embodiment, the step ofdepositing the first layer is carried out at a temperature of 150-450°C., or of 150-350° C., or of 150-250° C., or of 200-250° C., or of200-230° C. In one embodiment, the step of depositing the intermediatelayer are carried out at a temperature of 150-450° C., or of 150-350°C., or of 150-250° C., or of 200-250° C., or of 200-230° C. In oneembodiment, the steps of depositing the first layer and of depositingthe intermediate layer are carried out at a temperature of 150-450° C.,or of 150-350° C., or of 150-250° C., or of 200-250° C., or of 200-230°C. The inventors of the present invention surprisingly found out thatthe use of the above deposition temperatures minimizes the growth ofharmful phases or orientation of the grown material or layer.

The thickness of the material or layer produced by the ALD-type processcan be increased by repeating several times a pulsing sequencecomprising the aforementioned pulses containing the precursor material,and the purging periods. The number of how many times this sequence,called the “ALD cycle”, is repeated depends on the targeted thickness ofthe layer. In one embodiment, the step of depositing the first layer iscarried out until the thickness of the first layer is 10-1000 nm, or50-500 nm, or 100-300 nm. In one embodiment, the thickness of the firstlayer is 10-1000 nm, or 50-500 nm, or 100-300 nm. In one embodiment, thestep of depositing the intermediate layer is carried out until thethickness of the intermediate layer is 0.1-50 nm, or 0.5-10 nm, or 1-5nm. In one embodiment, the thickness of the intermediate layer is 0.1-50nm, or 0.5-10 nm, or 1-5 nm. In one embodiment, the steps of depositingthe first layer and depositing the intermediate layer are repeated untilthe thickness of the film is at least 0.5 μm, or at least 2 μm, or atleast 5 μm, or at least 10 μm. In one embodiment, the thickness of thefilm is at least 0.5 μm, or at least 2 μm, or at least 5 μm, or at least10 μm.

In one embodiment, the method comprises depositing two or moreintermediate layers. In one embodiment, the plasma etch-resistant filmcomprises two or more intermediate layers. In one embodiment, the plasmaetch-resistant film comprises at least two intermediate layers with adistance of 10-1000 nm, or 50-500 nm, or 100-300 nm, in between.

In one embodiment, the method comprises depositing a predeterminednumber of first layers and a predetermined number of intermediate layersone upon the other in turns. In one embodiment, the method comprisesdepositing the intermediate layer on the first layer. In one embodiment,the method comprises forming a first layer on the intermediate layer. Inone embodiment, the method comprises depositing a first layer on theintermediate layer. In one embodiment, the method comprises depositingthe intermediate layer directly on the first layer. In one embodiment,the method comprises forming a first layer directly on the intermediatelayer. In one embodiment, the method comprises depositing a first layerdirectly on the intermediate layer.

The embodiments of the invention described hereinbefore may be used inany combination with each other. Several of the embodiments may becombined together to form a further embodiment of the invention. Amethod, a film or a use, to which the invention is related, may compriseat least one of the embodiments of the invention described hereinbefore.

An advantage of the method according to the present invention is that aplasma etch-resistant film having a dense or an essentially non-porousstructure can be formed. As the formed film has a dense structure, itscapability to resist the corrosive environment in a plasma chamber for along period of time is increased.

An advantage of the method according to the present invention is that anintermediate layer or a cut-off layer can be formed while keeping theoxide material as such the same as in the first layer, i.e. without theneed to introduce any layer of different material into the plasmaetch-resistant film.

An advantage of the method according to the present invention is thatthe use of an ALD-type process enabling the formation of an amorphousintermediate layer or so-called cut-off layer allows the fabrication ofthick plasma etch-resistant film which does not crack or delaminate fromthe surface of the substrate.

An advantage of the method according to the present invention is thatthe use of the ALD-type process enables a controlled and reliable methodfor producing the plasma etch-resistant film in a one-step process bysimply changing the precursors for oxygen from one to another during thedeposition process.

EXAMPLES

Reference will now be made in detail to the embodiments of the presentinvention, an example of which is illustrated in the accompanyingdrawing.

The description below discloses some embodiments of the invention insuch a detail that a person skilled in the art is able to utilize theinvention based on the disclosure. Not all steps of the embodiments arediscussed in detail, as many of the steps will be obvious for the personskilled in the art based on this specification.

For reasons of simplicity, item numbers will be maintained in thefollowing exemplary embodiments in the case of repeating components.

As presented above the ALD-type process is a method for depositinguniform and conformal films or layers over substrates of various shapes.Further, as presented above in ALD-type processes the layer or film isgrown by alternately repeating, essentially self-limiting, surfacereactions between a precursor and a surface to be coated. The prior artdiscloses many different apparatuses suitable for carrying out anALD-type process. The construction of a processing tool suitable forcarrying out the methods in the following embodiments will be obvious tothe skilled person in light of this disclosure. The tool can be e.g. aconventional ALD tool suitable for handling the process chemicals. Manyof the steps related to handling such tools, such as delivering asubstrate into the reaction space, pumping the reaction space down to alow pressure, or adjusting gas flows in the tool if the process is doneat atmospheric pressure, heating the substrates and the reaction spaceetc., will be obvious to the skilled person. Also, many other knownoperations or features are not described here in detail nor mentioned,in order to emphasize relevant aspects of the various embodiments of theinvention.

The method of FIG. 1 and the structure of FIG. 2 illustrate,respectively, a method and the corresponding structure according to oneembodiment of the invention. The method of FIG. 1 presents how to carryout the method for fabricating a plasma etch-resistant film 1 on thesurface of a substrate 2 according to one embodiment of the presentinvention. This exemplary embodiment of the present invention begins bybringing the substrate 2 into the reaction space (step 1) of a typicalreactor tool, e.g. a tool suitable for carrying out an ALD-type processas a batch-type process. The reaction space is subsequently pumped downto a pressure suitable for forming a plasma etch-resistant film 1, usinge.g. a mechanical vacuum pump, or in the case of atmospheric pressureALD systems and/or processes, flows are typically set to protect thedeposition zone from the atmosphere. The substrate 2 is also heated to atemperature suitable for forming the film 1 by the used method. Thesubstrate 2 can be introduced to the reaction space through e.g. anairtight load-lock system or simply through a loading hatch. Thesubstrate 2 can be heated in situ by e.g. resistive heating elementswhich also heat the entire reaction space or ex situ.

After the substrate 2 and the reaction space have reached the targetedtemperature and other conditions suitable for deposition, the surface ofthe substrate can be conditioned in step 1 such that the differentlayers 3, 4 may be essentially directly deposited on the surface. Thisconditioning of the surface commonly includes chemical purification ofthe surface of the substrate 2 from impurities and/or oxidation. Also aconditioning thin film, such as a thin film of Al₂O₃ grown by ALD, maybe formed on its surface to form a part of the substrate. Theconditioning thin film may denote a material that covers any variationin the chemicals composition or crystallinity on the surface of thesubstrate, prevents possible diffusion of harmful impurity ions from thesubstrate to a subsequent coating, improves the adhesion of a subsequentcoating on its surface and/or makes the surface more suitable foruniform ALD thin film growth. Especially removal of oxide is beneficialwhen the surface has been imported into the reaction space via anoxidizing environment, e.g. when transporting the exposed siliconsurface from one deposition tool to another. The details of the processfor removing impurities and/or oxide from the surface of the siliconsubstrate will be obvious to the skilled person in view of thisspecification. In some embodiments of the invention the conditioning canbe done ex-situ, i.e. outside the tool suitable for ALD-type processes.An example of an ex-situ conditioning process is etching for 1 min in a1% HF solution followed by rinsing in DI-water. Another example of anex-situ conditioning process is exposing the substrate to ozone gas oroxygen plasma to remove organic impurities from the substrate surface inthe form of volatile gases.

After the surface of the substrate 2 has been conditioned, an alternateexposure of the deposition surface to different chemicals is started, toform a plasma etch-resistant film 1 directly on the surface of thesubstrate 2.

The precursors are suitably introduced into the reaction space in theirgaseous form. This can be realized by first evaporating the precursorsin their respective source containers which may or may not be heateddepending on the properties of the precursor chemical itself. Theevaporated precursor can be delivered into the reaction space by e.g.dosing it through the pipework of the reactor tool comprising flowchannels for delivering the vaporized precursors into the reactionspace. Controlled dosing of vapor into the reaction space can berealized by valves installed in the flow channels or other flowcontrollers. These valves are commonly called pulsing valves in a systemsuitable for ALD-type deposition.

Also other mechanisms of bringing the substrate 2 into contact with achemical inside the reaction space may be conceived. One alternative isto make the surface of the substrate (instead of the vaporized chemical)move inside the reaction space such that the substrate moves through aregion occupied by a gaseous chemical.

A reactor suitable for ALD-type deposition comprises a system forintroducing carrier gas, such as nitrogen or argon into the reactionspace such that the reaction space can be purged from surplus chemicaland reaction by-products before introducing the next chemical into thereaction space. This feature together with the controlled dosing ofvaporized precursors enables alternately exposing the surface of thesubstrate to precursors without significant intermixing of differentprecursors in the reaction space or in other parts of the reactor. Inpractice the flow of carrier gas is commonly continuous through thereaction space throughout the deposition process and only the variousprecursors are alternately introduced to the reaction space with thecarrier gas. Obviously, purging of the reaction space does notnecessarily result in complete elimination of surplus precursors orreaction by-products from the reaction space but residues of these orother materials may always be present.

Following the step of various preparations (step 1 discussed above), inthe embodiment of the present invention shown in FIG. 1, step a) iscarried out; i.e. the first layer of rare earth metal oxide is depositedon the deposition surface by exposing the deposition surface toalternately repeated surface reactions of a precursor for rare earthmetal and a first precursor for oxygen such that the structure of theformed first layer is crystalline. I.e. a layer of rare earth metaloxide is formed on the surface of the substrate. The rare earth metaloxide of the first layer is crystalline rare earth metal oxide. Thefirst layer 3 can be deposited by exposing, in step a1, the surface ofthe substrate 2 to a precursor for rare earth metal, such as (MeCp)₃Y.Exposure of the surface to the precursor for rare earth metal results inthe adsorption of a portion of the introduced precursor, e.g. (MeCp)₃Y,onto the surface of the substrate. After purging of the reaction space,the deposition surface is exposed to a first precursor for oxygen, suchas water. Subsequently, the reaction space is purged again. Some of thefirst precursor for oxygen in turn gets adsorbed onto the surface, inthe above step a2.

The order of exposing the deposition surface to the above precursors mayvary and the deposition surface could equally well be firstly exposed tothe first precursor for oxygen instead of the above mentioned order offirstly exposing the deposition surface to the precursor for a rareearth metal.

The above cycle of step a1 and step a2 can be repeated until apredetermined thickness of a first layer 3 is formed on the surface ofthe substrate. Then the process is continued in step b) by depositing anintermediate layer 4, which in this embodiment is an intermediate layerof a mixture of rare earth metal oxide and rare earth metal carbonatecontaining at least one inorganic carbonate group CO₃, on the firstlayer formed in step a).

The intermediate layer is deposited on the deposition surface byexposing the deposition surface to alternately repeated surfacereactions of a precursor for rare earth metal and a second precursor foroxygen such that the structure of the formed intermediate layer 4 isamorphous. I.e. the intermediate layer is formed on the surface of thefirst layer 3. The intermediate layer 4 can be deposited by exposing, instep b1, the deposition surface i.e. now the surface of the first layer3, to a precursor for rare earth metal, such as (MeCp)₃Y. Exposure ofthe surface to the precursor for rare earth metal results in theadsorption of a portion of the introduced precursor, e.g. (MeCp)₃Y, ontothe deposition surface. After purging of the reaction space, thedeposition surface is exposed to a second precursor for oxygen, such asozone. Subsequently, the reaction space is purged again. Some of thesecond precursor for oxygen in turn gets adsorbed onto the surface, inthe above step b2.

The order of exposing the deposition surface to the above precursors mayvary and the deposition surface could equally well be firstly exposed tothe second precursor for oxygen instead of the above mentioned order offirstly exposing the deposition surface to the precursor for a rareearth metal.

The above cycle of step b1 and step b2 can be repeated until apredetermined thickness of the intermediate layer 4 is formed on thedeposition surface.

Each exposure of the deposition surface to a precursor in step a) orstep b), according to the embodiment of FIG. 1, results in formation ofadditional deposit on the deposition surface as a result of adsorptionreactions of the corresponding precursor with the deposition surface.Thickness of the plasma etch-resistant film 1 on the surface of thesubstrate 2 can be increased by repeating step a) and/or step b) one ormore times. The thickness of the film is increased until a targetedthickness is reached, after which the alternate exposures are stoppedand the process is ended. As a result of the deposition process a plasmaetch-resistant film is formed on the surface of the substrate havingdistinct layers with different structures. The plasma etch-resistantfilm also has excellent thickness uniformity and compositionaluniformity along the deposition surface.

The following example describes how a plasma etch resistant film can befabricated on a surface of a substrate.

Example 1 Fabricating a Plasma Etch-Resistant Film on a Surface of aSubstrate

A plasma etch-resistant film was formed on the surface of a substrateaccording to an embodiment of the present invention shown in FIG. 1.

In this example a piece of metal with machined features including deepholes was used as a substrate. The substrate was placed into thereaction chamber of a TFS200 ALD reactor. The reaction chamber waspumped to vacuum with a mechanical vacuum pump connected to the exhaustline of the reaction chamber. The pressure of the reaction chamber wasadjusted to about 1-2 mbar with the vacuum pump and a continuous flow ofnitrogen gas that had a purity of at least 99.9999 vol-% (purity≥6.0).The temperature of the reaction chamber was adjusted to the depositiontemperature with PID-controlled electrical resistance heaters. Thedeposition temperature was 220° C. As a conditioning step, the surfaceof the substrate was first covered with a layer of aluminium oxidehaving a thickness of 10 nm and referred to as a conditioning thin film,grown at 220° C. from trimethylaluminum (TMA) and water by the ALD-typemethod. The conditioning thin film thus formed part of the substrate, onthe surface of which the plasma etch-resistant film was formed.

In this example tris(methylcyclopentadienyl)yttrium was used as theprecursor for yttrium.

Water kept in an external liquid precursor source in controlled fluidcommunication with the reaction chamber was used as the first precursorfor oxygen. Water had sufficiently high vapor pressure at 20° C. to bepulsed without additional nitrogen carrier gas to the reaction chamber.

A combination of ozone and oxygen gas, generated from oxygen gas with aBMT 803N ozone generator, was used as the second precursor for oxygen.The ozone generator was in controlled fluid communication with thereaction chamber.

The tris(methylcyclopentadienyl)yttrium was heated to 134° C. in anexternal precursor source to generate adequate vapor pressure of theprecursor for yttrium. The external yttrium precursor source was incontrolled fluid communication with a nitrogen gas source and thereaction chamber. Nitrogen gas introduced from a nitrogen gas source tothe yttrium precursor source was used as a carrier gas for the yttriumprecursor vapor.

The first pulsing sequence for forming the first layer (Y₂O₃ layer)consisted of the following steps: yttrium precursor vapor pulse, a firstnitrogen gas purge, water vapor pulse and a second nitrogen gas purge.The mixture of the nitrogen gas and yttrium precursor vapor formedinside the precursor source was pulsed for 2 s to the reaction chamberwhere the substrate with reactive hydroxyl sites on the surface wasexposed to the yttrium precursor vapor that left chemisorbed yttriumprecursor species on the substrate surface. After the yttrium precursorvapor pulse, the reaction chamber was purged with nitrogen gas for 5 s.After the first purge step water vapor was pulsed to the reactionchamber for 0.15 s to form a hydroxylated yttrium oxide surface from theyttrium precursor species chemisorbed on the substrate surface. Afterthe water vapor pulse the reaction chamber was purged with nitrogen gasfor 7 s to remove surplus precursor and reaction by-products from thereaction chamber. The pulsing sequence was repeated 1550 times to formthe first layer having a thickness of about 200 nm.

Next, the intermediate layer was deposited by repeating a second pulsingsequence 16 times, wherein the second pulsing sequence consisted of thefollowing steps: yttrium precursor vapor (tris(methylcyclopentadienyl)yttrium vapor) pulse (2 s), a first nitrogen gas purge (5 s),oxygen/ozone gas pulse (0.5 s) and a second nitrogen gas purge (7 s).The deposited intermediate layer consisted of a mixture of yttriumoxide, yttrium carbonate and yttrium oxycarbonate, in other words themixture being Y₂O_(x)(CO₃)_(3-x), wherein x=0-3.

The deposition of the first layer and the intermediate layer wasrepeated 10 times to form a plasma etch-resistant film having athickness of about 2.0 μm.

After the deposition process the coated substrate was cooled to roomtemperature. The plasma etch-resistant film had good adhesion to thesubstrate. A cross sectional FE-SEM images of FIG. 3 depicted that theplasma etch-resistant film was conformal and covered all external andinternal surfaces machined to the substrate. No cracks or pinholes werefound in the plasma etch-resistant film.

X-ray diffraction (XRD) patterns revealed that the plasma etch-resistantfilm consisted of cubic yttrium oxide (Y₂O₃) having low fracturepropensity (222) and (440) crystal orientations. It was also noticedfrom the XRD patterns that the intermediate layers had eliminated highfracture propensity monoclinic Y₂O₃ phase and cubic (400)-oriented Y₂O₃phase from this plasma etch-resistant film made by the method accordingto the present invention.

Examples 2-6 Fabricating a Plasma Etch-Resistant Film on a Surface of aSubstrate

In the above example 1 tris(methylcyclopentadienyl)yttrium was used asthe precursor for yttrium, water was used as the first precursor foroxygen, and a combination of ozone and oxygen was used as the secondprecursor for oxygen. However, as is obvious for the person skilled inthe art based on the above specification, also other first precursorsfor oxygen, other second precursors for oxygen and other precursors forrare earth metal can be used. In the below table 1 examples of forming aplasma etch-resistant film on a surface of a substrate according to someembodiments of the present invention are presented.

TABLE 1 Parameters used for fabricating a plasma etch- resistant film ona surface of a substrate Precursor First Second Deposi- Material forrare precursor precursor tion of the earth for for temper- intermediatemetal oxygen oxygen ature layer Exam- Cp₃Y H₂O O₃ 230° C.Y₂O_(x)(CO₃)_(3−x), ple 2 x = 0-3 Exam- (EtCp)₃Y H₂O O₃ 240° C.Y₂O_(x)(CO₃)_(3−x), ple 3 x = 0-3 Exam- (MeCp)₃Y H₂O CO₂ 230° C.Y₂O_(x)(CO₃)_(3−x), ple 4 plasma x = 0-3 Exam- (^(i)PrCp)₃Y H₂O O₃ 240°C. Y₂O_(x)(CO₃)_(3−x), ple 5 x = 0-3 Exam- (MeCp)₃Er H₂O O₃ 240° C.ErO_(x)(CO₃)_(3−x), ple 6 x = 0-3 Exam- Cp₃Sc H₂O O₃ 230° C.ScO_(x)(CO₃)_(3−x), ple 7 x = 0-3

It is obvious to a person skilled in the art that with the advancementof technology, the basic idea of the invention may be implemented invarious ways. The invention and its embodiments are thus not limited tothe examples described above; instead they may vary within the scope ofthe claims.

The invention claimed is:
 1. A method for fabricating a plasmaetch-resistant film on a surface of a substrate, wherein the methodcomprises the step of forming a film comprising an intermediate layer ofrare earth metal oxide, rare earth metal carbonate, or rare earth metaloxycarbonate or any mixture thereof on a first layer of rare earth metaloxide, wherein the rare earth metal is the same in the first layer andin the intermediate layer, and wherein the step of forming the filmcomprises, in a reaction space, the steps of: depositing the first layerby exposing a deposition surface to alternately repeated surfacereactions of at least two precursors including a precursor for rareearth metal and a first precursor for oxygen such that the structure ofthe first layer is crystalline, and depositing the intermediate layer byexposing a deposition surface to alternately repeated surface reactionsof at least two precursors including a precursor for rare earth metaland a second precursor for oxygen such that the structure of theintermediate layer is amorphous, wherein the first precursor for oxygenis different from the second precursor for oxygen.
 2. The method ofclaim 1, wherein the method comprises depositing the intermediate layeron the first layer such that the surface of the first layer is coveredby the intermediate layer.
 3. The method of claim 1, wherein thedeposition surface is exposed to carbon dioxide simultaneously withbeing exposed to the second precursor for oxygen or after being exposedto the second precursor for oxygen.
 4. The method of claim 1, whereinthe first precursor for oxygen is selected from a group consisting ofwater, methanol, ethanol, propanol, isopropanol, butanol, 2-butanol, andtert-butanol.
 5. The method of claim 1, wherein the second precursor foroxygen is selected from a group consisting of ozone; and a combinationcomprising ozone.
 6. The method of claim 1, wherein the second precursorfor oxygen is selected from a group consisting of a combination of ozoneand water; a combination of ozone and oxygen; and a combination of ozoneand hydrogen peroxide.
 7. The method of claim 1, wherein the secondprecursor for oxygen is selected from a group consisting ofoxygen-containing radicals; oxygen plasma; carbon dioxide plasma;organic peroxides; organic hydroperoxides; peroxyacids; and singletoxygen.
 8. The method of claim 1, wherein the precursor for rare earthmetal is selected from a group consisting of a precursor for scandium, aprecursor for yttrium, a precursor for lanthanum, a precursor forcerium, a precursor for praseodymium, a precursor for neodymium, aprecursor for samarium, a precursor for europium, a precursor forgadolinium, a precursor for terbium, a precursor for dysprosium, aprecursor for holmium, a precursor for erbium, a precursor for thulium,a precursor for ytterbium, and a precursor for lutetium.
 9. The methodof claim 1, wherein the steps of depositing the first layer anddepositing the intermediate layer are carried out by using the sameprecursor for rare earth metal, or wherein the steps of depositing thefirst layer and depositing the intermediate layer are carried out byusing different precursors for rare earth metal.
 10. The method of claim1, wherein the steps of depositing the first layer and depositing theintermediate layer are carried out at a temperature of 150 to 450° C.11. The method of claim 1, wherein the step of depositing the firstlayer is carried out until the thickness of the first layer is between10 and 1000 nm.
 12. The method of claim 1, wherein the step ofdepositing the intermediate layer is carried out until the thickness ofthe intermediate layer is between 0.1 and 50 nm.
 13. The method of claim1, wherein the steps of depositing the first layer and depositing theintermediate layer are repeated out until the thickness of the film isat least 0.5 μm.
 14. A plasma etch-resistant film on a surface of asubstrate obtainable by the method of claim
 1. 15. The method of claim1, wherein the steps of depositing the first layer and depositing theintermediate layer are carried out at a temperature of 200 to 230° C.16. The method of claim 1, wherein the steps of depositing the firstlayer and depositing the intermediate layer are carried out at atemperature of 200 to 250° C.
 17. The method of claim 1, wherein thesteps of depositing the first layer and depositing the intermediatelayer are carried out at a temperature of 150 to 250° C.
 18. The methodof claim 1, wherein the steps of depositing the first layer anddepositing the intermediate layer are carried out at a temperature of150 to 350° C.
 19. The method of claim 1, wherein the step of depositingthe first layer is carried out until the thickness of the first layer isbetween 100 and 300 nm.
 20. The method of claim 1, wherein the step ofdepositing the first layer is carried out until the thickness of thefirst layer is between 50 and 500 nm.
 21. The method of claim 1, whereinthe step of depositing the intermediate layer is carried out until thethickness of the intermediate layer is between 0.5 and 10 nm.
 22. Themethod of claim 1, wherein the step of depositing the intermediate layeris carried out until the thickness of the intermediate layer is between1 and 5 nm.
 23. The method of claim 1, wherein the steps of depositingthe first layer and depositing the intermediate layer are repeated outuntil the thickness of the film is at least 2 μm.
 24. The method ofclaim 1, wherein the steps of depositing the first layer and depositingthe intermediate layer are repeated out until the thickness of the filmis at least 5 μm.
 25. The method of claim 1, wherein the steps ofdepositing the first layer and depositing the intermediate layer arerepeated out until the thickness of the film is at least 10 μm.